1. Field of the Invention
Aspects of the present invention relate to a wireless data communication system, and more particularly, to preceding in a Multiple-input Multiple-Output (MIMO) system.
2. Description of the Related Art
Precoding is a process of appropriately allocating users to each spatial beam in a space-division multiple access (SDMA) Multiple-Input Multiple-Output (MIMO) scheme.
Programmable preceding techniques are discussed in C30-20061030-064 draft that was published in a 3rd Generation Partnership Project 2 Ultra Mobile Broadband (3GPP2 UMB) standardization conference for next generation mobile communication. According to the C30-20061030-064 draft, a preceding matrix consists of a combination of clusters, and each terminal feeds back indexes of a table to a base station. In this instance, the table includes overlapping clusters.
However, it is difficult to calculate channel quality information (CQI) with respect to all available clusters. Accordingly, there is a need for some constraint on CQI for a simple calculation.
Also, when a base station determines a codebook, a terminal must unconditionally download the codebook without knowing a reliability and characteristics of the codebook. Accordingly, there is a need to form a feedback route so that the terminal can pre-verify the characteristics of the codebook, or so that the terminal can affect the characteristic of the codebook.
Also, conventional preceding techniques can be effective for a single user. However, the conventional precoding techniques have limitations in regards to allocating spatial beams in a multi-user communication system. Accordingly, there is a need for a development of a method to generate an effective programmable codebook in a preceding process for a MIMO system.